1. Field of the Invention
The present invention relates to facsimile communications between standard facsimile apparatuses, and more particularly to facsimile communications through a communication network composed of networks with good transmission quality, such as a wire system subnetwork, and of subnetworks with relatively bad transmission quality, such as an open-wire carrier circuit and a mobile system network, the foregoing subnetworks of good and bad quality being interspersed in the communication network between the facsimile apparatuses.
Communications between facsimile apparatuses are primarily achieved conventionally through a wire system network, such as a public data network (PDN), an integrated services digital network (ISDN), a public switched data network (PSDN) or a facsimile communication network (FICS), with equipment for use in the above networks. International standards for example the CCITT Recommendations, facsimile communications through a wire system network in particular. Standard facsimile systems, enjoying wide application over domestic and overseas areas, adopt the international standards or at least a standards based thereupon. However such standards are designed for a wire system network with relatively good transmission quality, without having any protection against the occurrence of noises and broken lines, e.g., a powerful error correcting function.
Automobile telephones and other mobile networks suffer from a variety of disturbances because of their inclusion of mobile radio channels. These disturbances include internal noises emitted from radio transmitter-receiver units (TRU), urban noises such as multipath phasing and shadowing which occur during propagation of electric waves and the effect on control signals and voice channels of the hand-off procedure peculiar to a cellular system, which would severely reduce the quality of a network with regard to facsimile communications. The use of conventional standard facsimile devices therefore results in deteriorated image quality or frequent interruptions of communications, as reported in "Experimental Facsimile Signal Transmission in Mobile Communication channels", Omori and Kinoshita, No. 2432, the Unified Meeting of the Society of the Electro Communication, 1984.